docs: def orbit(self, orbit):
          """Initialize the propagator
  
          Args:
              orbit (Orbit)
          """
  
          self._orbit = orbit
          tle = Tle.from_orbit(orbit)
          lines = tle.text.splitlines()
  
          if len(lines) == 3:
              _, line1, line2 = lines
          else:
              line1, line2 = lines
  
          self.tle = twoline2rv(line1, line2, wgs72)